Device for screening off lines of electric flux in an installation for electrolytically processing essentially flat elements (III)

ABSTRACT

The invention relates to a device for screening off lines of electric flux in an installation for electrolytic processing of substantially plate-shaped material in the form of one or more workpieces which is held underneath a goods carrier and immersed in a bath when the goods carrier is lowered. A screen is provided which is adjustable in the vertical direction by a hold-down mechanism which is coupled with the movement of the goods carrier. The hold-down mechanism includes rods which project downward from the goods carrier to bear on two end regions of the screen. The lower ends of the rods and the end regions of the screen are constructed in such a way that the screen cannot be displaced relative to the rods at least in its longitudinal direction. The distance between the rods is greater than the width of the material to be processed which is located between the rods during processing. An apparatus is provided for transporting the screen from the lower working position into an upper parking position, the material to be processed hangs down from the goods carrier without lateral holders, and there are no guides between the bath vessel and screen.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a device for screening off lines of electricflux in an installation for electrolytic processing of substantiallyplate-shaped material in the form of one or more workpieces which isheld underneath a goods carrier and immersed in a bath when the goodscarrier is lowered. A screen is provided which is adjustable in thevertical direction by hold-down means and screens off theabove-mentioned lines of electric flux at the lower region of thematerial to be processed in the course of operation, the hold-down meansbeing coupled with the movement of the goods carrier. Its preferred useis for electroplating printed circuit boards. The invention could alsobe used for processing other, similar workpieces and in otherinstallations for electrolytic processing, e.g. for carrying outelectrophoresis to apply thin, photo-sensitive films on printed circuitboards.

2. Discussion of the Prior Art

A device constructed for screening off lines of electric flux in anelectroplating installation is disclosed in the subsequently publishedDE-OS 40 05 209 which describes, among other things, a construction witha lower pair of screens which arc constructed as floating bodies and arcsituated on both sides of the lower region of a plate-shaped material tobe electroplated. They are brought into the desired lower screening offposition by hold-down means. Those hold-down means are fastened to framerods, between which the plate shaped material to be electroplated issupported, and are moved down along with the downward movement of thegoods carrier. However, the aforementioned screens which are constructedas floating bodies can only be moved up out of their lower position by arelatively short distance, since they are prevented from a continuedupward movement by a stop. It is also possible to raise these lowerscreens in a corresponding manner by means of a pull cable. The lowerscreens mentioned above are also guided at the bath vessel so as to beadjustable in the vertical direction. This is also true of the upperscreens which are likewise provided. DE-OS 40 05 209 mentions that theinvention can be used when the workpieces to be electroplated aresuspended at the goods carrier by clamps or the like or also inarrangements in which the workpieces to be processed are held betweenframe rods of carrying racks which are attached in turn to the goodscarrier. However, the aforementioned construction of two bold-down meanswhich press down the lower pair of screens is disclosed only in the formof two hold-down parts at frame rods of a carrying rack. In the subjectmatter of DE-OS 40 05 209, the force for moving the screens down isapplied by the hold-down means, i.e. the plate-shaped material to beprocessed is not loaded by this force. However, a disadvantage consistsin the relatively costly, bulky construction of the two screens andparticularly in the requirement that the screens be guided in the bathvessel in the vertical direction by their ends.

Another device for screening off lines of electric flux in anelectroplating installation is known from JP 55-145 199 A in PatentAbstracts of Japan, Sect. C, Vol. 5 (1981) No. 16 (C-41). In this case,a screen is provided in a shielding and positioning frame for suchprinted circuit boards in immersion electroplating installations. Thescreen is constructed like the ridge of a roof and is guided by lateraltabs into vertically extending slots of a holder. The "ridge" of this"roof" faces downward. In its initial position, this screen is situatedon the surface or upper region of the bath. The printed circuit board tobe processed is inserted from above into the interior of the "roof" byits lower edge and carries the screen down with it during the immersionprocess. This screen prevents so-called scorching, i.e. unwantedadditional metallization deposits in the lower edge region of theaforementioned printed circuit board. This arrangement of the prior arthas a number of disadvantages. The screen must be pressed down by way ofthe printed circuit board to be processed. But such printed circuitboards are often very thin so that they cannot transmit the forcesrequired for pressing down without sustaining damage. In such cases, theprinted circuit boards buckle outward under the influence of thepressing pressure, which can damage these sensitive boards and lead todeposits of irregular thickness on their convex and concave sides. Anarrangement corresponding to the aforementioned screening off device isknown from DE-PS 37 26 571. A similar arrangement with lateral guides ofthe screen at the bath vessel is known from U.S. Pat. No. 4,879,007.

SUMMARY OF THE INVENTION

The object upon which the present invention is based proceeds from adevice as discussed above. While retaining the advantage achieved by thehold-down means, i.e. that the material to be processed is not actedupon by the force for pressing down the screens, a device according tothe present invention is to be constructed so as to avoid thedisadvantages of a guide of the screen in the bath vessel in a simple,space-saving construction.

This object is met in that the hold-down means are rods which projectdownward from the goods carrier and are constructed so as to bear on thetwo end regions of the screen, the lower ends of the rods and the endregions of the screen on which these ends of the rods bear beingconstructed in such a way that the screen cannot be displaced relativeto the rods at least in its longitudinal direction. Furthermore, thedistance between the rods is greater than the width of the material tobe processed which is located between the rods during processing, andmeans are provided for transporting the screen from the lower working:position into an upper parking position. Additionally, the material tobe processed hangs down from the goods carrier without lateral holders,and there are no guides between the bath vessel and screen. Theadvantage of dispensing with guides of the screen at or in the bathvessel consists in that the space which they would otherwise occupy isnow available. The space which is now available in the width directionof the vessel is used to accommodate the rods. Thus, the rods providethe advantage of pressing down the screen without requiring additionalspace. This force for moving the screen out of the parking position intothe working position does not load the material to be processed. This iscritically important particularly in the principle area of applicationof the invention, namely thin printed circuit boards, since these boardsare, for practical purposes, incapable of absorbing or transmittingconsiderable forces acting in their longitudinal direction. When thegoods carrier is lowered, the two rods with the screen and the materialto be processed which is located between the rods are also moved downinto the working position simultaneously. A further advantage inomitting the guides between the ends of the screen and the bath vesselconsists in that such guides are difficult to arrange at the bathvessel, particularly in bath vessels produced from steel, which arecommonly provided with an anti-corrosive coating. Such an anticorrosivecoating has irregular thickness and also an irregular surface, for whichreason they themselves are not suitable for guiding the screens. On theother hand, it would be difficult to fasten separate guide strips, e.g.of plastic, at surfaces of the bath vessel which are coated in thismanner. According to the aforementioned teaching of the presentinvention, the function of the guides formerly provided at the bathvessels :is taken over by the ends of the rods. Thus, these rods andtheir ends serve a dual purpose, namely to press the screen down intothe working position and also to guide them. This is advantageous interms of function and beyond this serves to simplify the constructionand, as already mentioned, to save space inside the bath vessel. Thematerial to be processed and the rods cannot collide with one another asthe distance between the rods is greater than the width of the materialto be processed. An added advantage is provided by the further teachingof the invention, that the material to be processed can hang down freelydirectly from the goods carrier without being held laterally, which alsofacilitates the attachment of the goods for electrolytic processing aswell as the subsequent removal of the goods. The above-mentionedadvantages also apply in comparison to the prior art according to JP55-145 199A and DE-PS 37 26 571.

Further, means are provided for transporting and removing the screenfrom the lower working position into the upper parking position. Suchmeans include constructing the screen as a float or providing flatingbodies that bring the screen out of the working position in the bathliquid into the parking position. The screen can also be connected toweights or springs located outside the bath vessel which lift the screeninto its parking position after the material has been processed and therods have been raised.

In a further embodiment of the invention, the position of the screen inthe upper parking position is secured and, the screen is secured againstaccidental shifting by simple abutments provided in the upper region ofthe bath for determining the upper parking position of the screen andholding it in this position. These abutments are narrow along thevertical and therefore have small longitudinal dimensions along thevertical. They need only be fastened at the upper edge of the vesselwhich does not come into contact with the bath liquid.

In another embodiment the screen can be guided and supported by the endsof the rods. In this embodiment, the end regions of the screen havestops or abutments at least in front of and behind the lower ends of therods resting on the screen. The ends of the rods can also have aconnection piece at their underside while the screen is provided with aslot for receiving the connection piece.

In yet another embodiment of the invention, the screen holds the lowerregion of the material to be processed in the working position forelectrolytic processing by a slot so that it cannot shift out of thisvertical position unintentionally.

In still a further embodiment, the base of the slot of the screen issituated lower than the lower front edge of the material to be processedwhen the material is held in the working position, so that the screendoes not exert any pressure force against the lower region of thematerial to be processed.

Another embodiment of the invention includes directing means for theguidance of the screen by the rods and which facilitates the insertionof the workpiece into the screen.

In an additional embodiment, the rods are vertically adjustable at thegoods carrier and can be fastened in the desired vertical position toallow adaptation to goods of different lengths.

Furthermore, in yet a further embodiment, the screen has longitudinalribs and transverse plates which are located at least in end regions ofthe screen. The ribs and plates being made of an electricallynon-conductive material.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages are shown in the following description and pertinentdrawings of embodiment examples according to the invention. Thesubstantially schematic drawing shows:

FIG. 1 is a side view of an arrangement according to the invention withthe screen, rod and material to be processed in the working position;

FIG. 2 is a front view of the arrangement in FIG. 1 according to arrowII in FIG. 1:

FIG. 3 shows only the screen in the parking position with a fullyelevated rod as viewed from the front according to arrow II;

FIG. 4 is a front view analogous to FIG. 3, but in which the rod hasmoved downward into the parking position of the screen; and

FIG. 5 shows another embodiment of the invention in a side viewanalogous to the side view of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A bath vessel 1, with a bath liquid 2, is shown in its entirety in FIG.1 and partially in the remaining figures. The bath level is designatedby 3. Two rods 5 are fastened to the goods carrier 4 and are immersed inthe bath 2 when the goods carrier 4 is lowered and are pulled out of thebath 2 again when the goods carrier 4 is raised (see double arrow 7 inFIG. 3). The material 8 to be processed is detachably suspended, e.g.via indicated clamps 9, at the goods carrier 4, hangs down freely fromthe latter, and is likewise immersed in or pulled out of the bath 2respectively along with the movement of the goods carrier 4 according tothe double arrow 7. The material to be processed, which is shown in ageneral way and designated by 8, can be a single workpiece or canconsist of a plurality of workpieces. The term "material to beprocessed" thus comprehends both of the above-mentioned possibilities.

Further, a screen 10 is provided into which the lower region 8' of thematerial to be processed projects during the processing (see FIGS. 1 and2). This prevents too many lines of electric flux from concentrating atthe lower region 8' of the goods during the processing phase (positionof parts according to FIGS. 1 and 2) and the formation of unwantedaccumulations of material deposited as a result of the electrolytic,e.g. electroplating, process.

The screen 10 can be moved up and down in the vertical direction inorder to arrive in the aforementioned working position according toFIGS. 1 and 2 in which it screens off a portion of the lines of electricflux relative to the lower region 8' of the goods. On the other hand,FIGS. 3 and 4 show the screen in the so-called parking position in whichit is located in the upper region of the bath, e.g. in the preferredconstruction with attached floats 11 at the surface of the bath 2. FIG.3 shows the uppermost position of one of the rods 5 (the goods carrier 4is not shown in FIGS. 3 and 4). A connection piece 12 which fits into aslot 13 of the screen is arranged at the lower ends 5' of the rods.Also, two projections 14 are provided at the lower ends 5' of the rodsand extend transversely to the longitudinal direction of the screen.When the goods carrier with the material 8 to be processed, e.g. aprinted circuit board, is lowered, this results in a correspondinglowering of the rods 5. The latter then arrive in the slot 13 with theirconnection pieces 12 and the projections 14 come to rest oncorresponding supports, e.g. upper end faces 15, of longitudinal ribs 16of the screen. This position is shown in FIG. 4. When the goods carrier4 is moved further downward, it moves the material 8 and the rods 5downward parallel and synchronously relative to one another, but nopressing force is exerted on the material 8 to be processed. The rods 5carry the screen 10 downward along with it out of its parking positionin FIGS. 3 and 4 until reaching the working position according to FIGS.1 and 2. In so doing, the material to be processed is held in its lowerregion 8' by a slot of the screen which approximately corresponds to andis flush with the slot 13 according to FIG. 3. The slot 13 andaccordingly also the slot in the screen receiving the material to beprocessed project downward far enough so that the lower narrow frontedge of the lower region 8' of the material to be processed does notstrike against the base of the slot 13 or the base of the correspondingslot in the screen when the projections 14 come to rest on thelongitudinal ribs 16. This ensures that no downwardly directed pressingforce is exerted on the material to be processed when introducing thismaterial 8 and particularly when processing it. The aforementioneddownward elongation of the slots ensures that the plate-shaped material8 cannot strike against the base of the slot.

The upper region 8" of the material 8 is held by suspension means, e.g.clamps 9. This has the advantage that the plate-shaped material 8participates in the so-called goods movement of the goods carrier, i.e.a reciprocating movement of the goods carrier and of the material 8 inthe direction of the double arrow 17 (see FIG. 3). However, the rods 5also cause the screen 10 and the lower end of the material 8 to beprocessed to move along with them synchronously. The longitudinal ribs16 and 20 can be provided with recesses so that the screen does notoffer excessive resistance to the movement in the liquid. To achieve thescreening off effect, the recesses in the screens 16 and 20 are offsetrelative to one another. The material 8 to be processed is preventedfrom warping in that its lower and upper regions 8', 8" are supported,even when long, relatively thin plates are concerned as is the case withthe printed circuit boards mentioned above. The height (length) of thematerial to be processed can vary and, e.g. in the case of aplate-shaped material 8 which is shorter than that shown in FIG. 1, thelower edge 8' of the material and the rod are not moved down as far aswould be necessary for processing a material having the length shown inFIG. 1. If necessary or if desired, the rods 5 can be verticallyadjustable relative to the goods carrier 4 and can be fixed in therespective vertical position (not shown in the drawing). In this case,i.e. with plate-shaped material of varying length, the screen 10occupies the position in which it shields the lower region 8' of thematerial against an excess of lines of electric flux in the workingposition. The longitudinal sides 8'" of the material to be processed arefree of holders, but the rods 5 can be constructed, e.g. provided withshields, in such a way that they shield the lateral edges of thematerial 8 against excessive concentrations of lines of electric fluxinsofar as this is not effected in some other way. Such shields areparticularly advantageous when the width of the material 8 to beprocessed varies.

The screen 10 can be moved out of the working position according toFIGS. 1 and 2, e.g. by detachable drivers (not shown in the drawing) ofthe rods 5, and back up into the parking position of FIGS. 3 and 4 andheld there by detachable means, likewise not shown in the drawing, atabutments 18 which are fastened at the edge 1' of the bath vessel 1. Ina preferred construction which is particularly simple with respect toboth design and function, the screen is constructed as a float or isprovided with the floats already mentioned. In the illustratedembodiment, these floats are sealed, roughly tubular floating bodies 11which are located at the longitudinal sides of the screen and aresecurely connected to them. The floating bodies 11 are dimensioned insuch a way that they impart a buoyancy to the screen 10 which causes itto move from the working position into the parking position by itself.In the parking position of FIG. 3, the floats 11 come to rest at angles19 of the abutments 18 and are accordingly held in the desired parkingposition automatically by their buoyancy. By raising the rods withconnection pieces 12 and projections 14, the rods are moved out of theposition according to FIG. 4 into the position according to FIG. 3 bythe goods carrier. The processed material 8 is simultaneously raisedalong with them and can be moved further by the goods carrier. FIG. 5shows another construction possibility of the invention in this respect.In this case, after the rods 5 are raised, the screen 10 is moved out ofthe working or processing position (upper position of the weights 22)into the upper parking position by means of weights 22 via pull cables23. For the sake of simplicity, the drawing shows only the correspondinglower position 22' of the weights 22 for the upper parking position, butnot the upper parking position of the screen.

The goods carriers with the material and rods are moved through theentire processing installation--from station to station--by means of atransporting device, not shown in the drawing.

The two end regions 10' of the screen 10 are suitably constructed forreceiving the lower ends 5' of the rods, at least for the possibility ofsupporting them. Moreover, the construction of the ends 10' of thescreen in this embodiment example, which has already been explained inpart, in combination with a corresponding construction of the lowerregions of the rods 5, is selected in such a way that the rods areimmovably mutually supporting in the longitudinal direction A as well asin the transverse direction B of the screen (see FIGS. 1 and 2) when therods bear on the screen. This is effected on the one hand in that theconnection piece 12 engages in the slot 13 (for holding in thetransverse direction B) and on the other hand in that the screen isshaped so as to provide directing means with adjoining openings for theinsertion of the ends of the rods and for holding their projections 14in the longitudinal direction A.

The screen can include a series of longitudinal ribs 20 which areconnected with one another at least in the end regions 10' by transverseplates 21. The longitudinal ribs 20 and the transverse plates 21 areproduced from materials which are not electrically conductive, e.g. aplastic. They have the cut out portions or slots for receiving the lowerregion 8' of the material and also for supporting and holding the ends5' of the rods for the purpose of preventing a displacement of thescreen relative to the rods in directions A and B.

We claim:
 1. A device for screening off lines of electric flux in aninstallation for electrolytic processing of substantially planarmaterial which hangs down from a goods carrier and is immersed in a bathvessel containing a bath liquid when the goods carrier is lowered, thedevice comprising:a screen which adjusts in a vertical direction andwhich screens off lines of electric flux at a lower region of thematerial to be processed, the screen having two end regions; hold-downmeans for vertically adjusting the screen, the hold-down means moveswith the goods carrier, the hold-down means including rods which projectdownward from the goods carrier to bear upon the two end regions of thescreen, the rods having lower ends which are constructed together withthe end regions of the screen so that the screen cannot be displacedrelative to the rods at least in a longitudinal direction of the screen,the rods are spaced at a distance that is greater than the completewidth of the material to be processed which is located between the rodsduring processing; and means for transporting the screen from a lowerworking position into an upper parking position so that the material tobe processed hangs down from the goods carrier without lateral holdersand so that no guides are present between the bath vessel and thescreen.
 2. A device according to claim 1, wherein the screen isconstructed as a float which has a buoyancy that brings the screen outof the working position in the bath liquid into the parking position. 3.A device according to claim 1, wherein said means for transporting thescreen from the working position into the parking position includesfloating bodies which are connected to the screen and have a buoyancythat brings the screen out of the working position in the bath liquidinto the parking position.
 4. A device according to claim 3, wherein thescreen has longitudinal sides, the floating bodies are arranged at thelongitudinal sides of the screen to project out therefrom.
 5. A deviceaccording to claim 1, wherein said transporting means includes weightsarranged outside the bath vessel and connected to the screen by cablesto lift the screen out of the working position into the parking positionafter the material has been processed and the rods have been raised. 6.A device according to claim 1, wherein the transporting means includessprings arranged outside the bath vessel and connected to the screen bycables to lift the screen out of the working position into the parkingposition after the material has been processed and the rods have beenraised.
 7. A device according to claim 1, and further comprisingabutments provided in an upper region of the bath, the abutments havingsupport faces for engaging the screen in the upper parking position, theabutments and support faces screening off lines of electric flux at anupper region of the material to be processed.
 8. A device according toclaim 1, and further comprising abutments provided in an upper region ofthe bath, the abutments having holding means for holding the screen inits upper parking position, the abutments and holding means screeningoff lines of electric flux at an upper region of the material to beprocessed.
 9. A device according to claim 1, wherein the end regions ofthe screen on which the lower ends of the rods bear are provided withabutments which adjoin the lower rod ends at least in front of andbehind the rod ends resting on the screen as viewed in the longitudinaldirection of the screen.
 10. A device according to claim 1, wherein theends of the rods have an underside provided with a connection piece, thescreen having a slot into which the connection piece of the rod ends isreceivable.
 11. A device according to claim 10, wherein the slot in thescreen has a base that is situated lower than a lower front edge of thematerial to be processed when the material is held in the workingposition.
 12. A device according to claim 10, wherein the lower ends ofthe rods have projections which extend transversely to the longitudinaldirection of the screen, the device further comprising means fordirecting insertion of the lower rod ends, connection pieces andprojections, the directing means are provided in the longitudinaldirection of the screen and in a transverse direction of the screen, thedirecting means also directing insertion of the material to be processedinto the slot of the screen.
 13. A device according to claim 1, whereinthe screen is provided with a slot in which a lower region of thematerial to be processed is held.
 14. A device according to claim 13,wherein the slot of the screen has a base that is situated lower than alower front edge of the material to be processed when the material isheld in the working position.
 15. A device according to claim 1, whereinthe rods are provided to be vertically adjustable at the goods carrierand fastenable in a vertical position.
 16. A device according to claim1, wherein the screen has longitudinal ribs and transverse plates, theplates are located at least in end regions of the screen.
 17. A deviceaccording to claim 16, wherein the longitudinal ribs and the transverseplates are made of an electrically non-conductive material.
 18. A deviceaccording to claim 17, wherein the longitudinal ribs and transverseplates are made of a plastic material.
 19. A device according to claim16, wherein the longitudinal ribs include two sets of longitudinal ribs,the screen is provided in its longitudinal ribs with recesses tofacilitate synchronous movement of the screen with the rods, therecesses of one set of longitudinal ribs are offset relative to therecesses of the other set of longitudinal ribs.
 20. A device accordingto claim 1, wherein the rods are constructed so that they shield lateraledges of the material to be processed from an excessive concentration oflines of electric flux.
 21. A device according to claim 1, wherein therods are provided with shields arranged to shield lateral edges of thematerial to be processed from an excessive concentration of lines ofelectric flux.